Cancer originates in fundamental genetic alterations in tumor cells, leading to changes in protein expression and function, finally resulting in characteristic "signatures" in the serum and on tumor cell surfaces. Powerful proteomics efforts are identifying sets of biomarkers that are characteristic of a tumor's innate biology, which will be important for prediction and monitoring of response to therapy. Since cancer development is a complex process requiring mutation and altered expression of multiple genes, full determination of the biological state and treatment susceptibility of a tumor will require assessment of numerous biomarkers in vivo. To address this issue, we turn to quantum dots (Qdots), which are tiny fluorescent nanocrystals that can be produced with a spectrum of defined emission wavelengths, for generation of multiplex detectors for biomarkers. In Aim 1, antibodies specific for well characterized biomarkers in prostate cancer and lymphoma, will be engineered and coupled to near-infrared Qdots developed in Project 5. Biophysical, biochemical, and biological properties of these tumor-specific Qdots. In Aim 2, we will extend the platform by using cell-surface markers in prostate cancer identified by Project 4, to produce recombinant targets and select novel antibodies by phage display for coupling to Qdots for multiplex imaging of multiple markers. Aim 3 will focus on biological modification of Qdots for targeting the alpha-v-beta3 integrin expressed on tumors and tumor neovasculature, using Arg-Gly-Asp peptides that bind specifically to this protein. Finally, in Aim 4 a strategy for amplifying Qdot signals will utilize coupling to peptides that will enhance cellular uptake, when their activity is unmasked by tumor-specific proteases. Throughout the project period, tumor-targeting Qdots will be provided for in vivo imaging in mouse therapy models of human cancer, to validate their utility. Tumor-specific Qdots will be invaluable reagents in cell biology and preclinical models, for in vivo, real time monitoring of tumor cell activity and function. Furthermore, the targeting strategies developed here can be extended to in vivo delivery of other classes of nanoparticles for alternative modes of detection or for therapy. A sophisticated understanding of the differences between tumor and normal tissues in living organisms will advance our understanding of how to detect and treat cancer.